upd
changed mobo(to ga 970a ds3p) and now it works fine, ~4k
could it be PCI bus thing?

upd2
if one of vc is in PCI ex1 slot both cards shows low hashrate and if both in PCI ex4-16 then both works fine.

Thanks for help, but did both, and still have low hashrate with 2 vc. normal with one.
Also tryed Adrenalin 18.6.1 instead of newest, updating mobo bios, putting vc in diff slots (both plugged via razers).

Miner works fine with one vc (vega56 2000 H/s).
But with 2 plugged it shows only half hashrate .
8GB ram, 60GB ssd swap, intel g4400, ASUS H110M-K D3
What could it be?